U.S. patent application number 09/917670 was filed with the patent office on 2003-02-06 for well tubing rotator and hanger system.
Invention is credited to Cuppen, Nolan.
Application Number | 20030024709 09/917670 |
Document ID | / |
Family ID | 25439163 |
Filed Date | 2003-02-06 |
United States Patent
Application |
20030024709 |
Kind Code |
A1 |
Cuppen, Nolan |
February 6, 2003 |
Well tubing rotator and hanger system
Abstract
In one aspect a rotating hanger comprises a dognut sleeve having
a bore and an outer profile compatible for support in the casing
bowl and sealing thereto and a tubular hanger mandrel fitted
rotatably to the dognut sleeve's bore and having an upper shoulder
projecting above the dognut sleeve for interaction with casing bowl
holddown screws which, when engaged, restrain rotation and prevent
ejection from the casing bowl. In another aspect, an improved well
tubing rotator and hanger system is provided the rotatable tubing
hanger, a tubular connector sub threaded to the hanger mandrel and
a rotator splined to the connector sub, the splined connector sub
enabling rotational coupling without imposing hanger loads into the
rotator which enables use of smaller, low profile and economical
rotators. In another aspect, a rotator having a threaded nozzle
wellhead connection is convertible to a flanged rotator.
Inventors: |
Cuppen, Nolan; (Calgary,
CA) |
Correspondence
Address: |
Sean W. Goodwin
Goodwin Berlin McKay
The Burns Building
237-8th Avenue S.E., Suite 360
Calgary
AB
T2G 5C3
CA
|
Family ID: |
25439163 |
Appl. No.: |
09/917670 |
Filed: |
July 31, 2001 |
Current U.S.
Class: |
166/382 ;
166/75.14; 166/85.4 |
Current CPC
Class: |
E21B 33/0355 20130101;
E21B 33/0415 20130101 |
Class at
Publication: |
166/382 ;
166/85.4; 166/75.14 |
International
Class: |
E21B 023/00 |
Claims
1. A rotating tubing hanger for suspending a string of tubing from
a casing bowl fitted with holddown screws comprising: a dognut
sleeve having a bore and an outer profile compatible for support by
the casing bowl and sealing thereto; and a tubular hanger mandrel
fitted rotatably to the dognut sleeve's bore and having a lower end
from which the tubing string is suspended and an upper end
projecting upwardly above the dognut sleeve for forming an upper
shoulder and positioned so that the holddown screws can be actuated
to engage the upper shoulder and prevent the hanger mandrel from
rotation and ejection from the casing bowl or can be actuated to
disengage from the upper shoulder.
2. The tubing hanger of claim 1 wherein the bore of the dognut
sleeve further comprises upward facing shoulder and the hanger
mandrel further comprises a outer and downward facing shoulder for
rotatable support on the dognut sleeve's upward facing
shoulder.
3. The tubing hanger of claim 2 wherein the hanger mandrel's upper
shoulder is positioned so that: the hanger mandrel is locked
against rotation and prevented from ejection when engaged by the
holddown screws; the hanger mandrel is free for rotation when the
holddown screws are disengaged from the upper shoulder; and both
hanger mandrel and dognut sleeve are free for removal from the
casing bowl when the holddown screws are fully disengaged.
4. The tubing hanger of claim 3 wherein the hanger mandrel's upper
shoulder is beveled so that when the holddown screws are engaged,
the upper shoulder is locked against rotation and restrained from
ejection from the casing bowl.
5. The tubing hanger of claim 4 wherein the bore of the upper end
of the hanger mandrel is threaded.
6. A rotator for a coupling with a rotating tubing hanger supported
in a casing bowl of a wellhead having a wellhead flange,
comprising: a flange housing for mounting to the wellhead flange,
said housing having a bore therethrough and a concentric
counterbore extending upwardly from a lower mounting face and
terminating at a top shoulder; a concentric ring gear supported in
the counterbore and sandwiched between the top shoulder and a lower
retaining ring, the ring gear having an inner diameter being fitted
with internal spline; a drive gear fitted to the flange housing for
rotatably driving the ring gear; a concentric and cylindrical
collar having an outer surface which is partially fitted with
splines compatible with and for rotational coupling with the ring
gear, and having an inner surface which is partially fitted with
splines for coupling with the rotating tubing hanger.
7. The rotator of claim 6 further comprising upper and lower
annular bushing rings positioned between the top shoulder and ring
gear and ring gear and retaining ring respectively.
8. The rotator of claim 7 further comprising seals between the
collar's outer surface and the counterbore below the ring gear the
collar's outer surface and the bore above the ring gear the collar
inner surface and the rotating tubing hanger above the tubing
hanger coupling.
9. The rotator of claim 6 wherein the flange housing has an upper
face and the bore extends into a threaded nozzle.
10. The rotator of claim 6 wherein the ring gear, drive gear and
collar are positioned between the lower and upper faces so that the
threaded nozzle can be machined off of the flange housing for
converting the upper face to a flanged mounting face.
11. An improved well tubing rotator and hanger system is provided
for a wellhead having a casing bowl, a wellhead flange, and
holddown screws actuable to extend into the casing bowl, said
system comprising: a rotatable two-piece tubing hanger having a
dognut sleeve supported in the casing bowl and having a bore, a
tubular hanger mandrel rotatable in the dognut sleeve's bore and
having an upper shoulder which, upon actuation of the holddown
screws, can be engaged by the holddown screws to lock rotation and
disengaged from the holddown screws to permit rotation of the
hanger mandrel and to permit removal of the rotating tubing hanger
from the casing bowl; a rotator mounted to the wellhead flange; and
a tubular connector sub, threaded at a lower end to the rotating
hanger and splined at an upper end for rotational-only coupling
with the rotator.
12. The improved system of claim 8 wherein the rotator comprises: a
flange housing for mounting to the wellhead flange, said housing
having a bore therethrough and a concentric counterbore extending
upwardly from a lower mounting face and terminating at a top
shoulder; an ring gear retained concentrically within the
counterbore, the ring gear being rotatable by a drive gear; and a
collar positioned concentric within the counter-bore and being
rotatable with the ring gear, and having an interface with the
connector sub so as transmit rotation from the ring gear to the
connector sub without incurring axial loads.
13. The improved system of claim 9 wherein the ring gear is
sandwiched between the top shoulder and a lower retaining ring has
an inner diameter being fitted with internal spline; the drive gear
is fitted to the flange housing for rotatably driving the ring
gear; the collar has an outer surface which is at least partially
fitted with splines compatible with and for rotational coupling
with the ring gear, and having an inner surface which is at least
partially fitted with splines for coupling with the connector
sub.
14. The improved system of claim 10 further comprising upper and
lower annular bushing rings positioned between the top shoulder and
ring gear and ring gear and retaining ring respectively.
15. The improved system of claim 8 further comprising seals between
the collar's outer surface and the counterbore below the ring gear
the collar's outer surface and the bore above the ring gear the
collar inner surface and the rotating tubing hanger above the
tubing hanger coupling.
16. The improved system of claim 8 wherein the hanger mandrel's
upper shoulder is positioned so that: the hanger mandrel is engaged
by the holddown screws when actuated into the casing bowl so as to
lock rotation of the hanger mandrel; the hanger mandrel is free for
rotation when the holddown screws are actuated so as to be
partially extracted from the casing bowl and are disengaged from
the upper shoulder; and both hanger mandrel and dognut sleeve are
free for removal from the casing bowl when the holddown screws are
fully disengaged.
17. A method for safely servicing a well's wellhead while avoiding
a blowout, the wellhead being fitted with a tubing rotator and a
casing bowl fitted with holddown screws, the method comprising:
providing a two-piece rotating hanger comprising a dognut sleeve
having a bore and an outer profile which is compatible for support
in the casing bowl and sealing thereto, and a tubular hanger
mandrel fifted rotatably to the dognut sleeve's bore, the mandrel
having a lower end from which a tubing string is suspended and an
upper end projecting upwardly above the dognut sleeve for forming
an upper shoulder and connected drivably to the tubing rotator;
actuating the holddown screws to a first position to engage the
hanger mandrel's upper shoulder for safely restraining rotation and
preventing ejection of the rotating hanger from the casing bowl;
and removing the tubing rotator.
18. The wellhead servicing method of claim 14 further comprising
relieving stored rotational energy in the tubing string by
actuating the holddown screws to disengage from the upper shoulder
and permitting the hanger mandrel to rotate.
19. The wellhead servicing method of claim 15 wherein once pressure
has been reduced below the tubing hanger the method further
comprises disengaging the holddown screws from the upper shoulder
sufficiently so that the hanger mandrel and dognut sleeve can be
removed fully from casing bowl.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to apparatus for mounting on a
wellhead for hanging and rotating a tubing string in a
wellbore.
BACKGROUND OF THE INVENTION
[0002] In a conventional oil well, a reciprocating or rotating
string of rods extends from a wellhead and down the bore of well
tubing extending downhole to a subterranean pump. Production well
fluids are conducted up the tubing. For various reasons, including
non-linearity of the well, the rod string and production tubing
periodically come into contact and the relative movement
therebetween eventually causes wear and even perforation of the
tubing with associated loss of production and an expensive
maintenance turnover.
[0003] A wellhead typically comprises a wellhead flange and casing
bowl secured at the top of a string of casing extending downhole.
The casing bowl supports tubing string extending down the casing.
The wellhead further comprises means to block the annulus, between
the casing and tubing string, and wellhead components secured to
the wellhead flange to handle production from the tubing string.
The tubing string is usually suspended from a tapered dognut or
hanger which is supported in the casing bowl under tubing string
weight. In an operating well, the annulus between the casing and
the tubing string is usually pressurized and to prevent annulus
pressure from lifting and ejecting the tubing string and hanger
from the bowl, one or more conventional holddown screws extend
radially inwardly from the casing bowl to engage the top of the
dognut.
[0004] Various apparatus are mounted on wellheads to allow slow
rotation of production tubing so as to distribute wear in the
tubing and thus extend the life of the tubing. Two main components
enable rotation and are used in a variety of configurations: a
rotatable tubing hanger which replaces the conventional dognut, and
a low-speed tubing rotator.
[0005] The configuration of the two components has been determined
to be very important. Some hangers and rotators are combined into a
unitary assembly such as applicant's own U.S. Pat. No. 5,964,286.
Others are further integrated into a specialized casing bowl which
supports the hanger. One disadvantage with a unitary assembly is
that to safely recover the hanger and rotator for maintenance or
for use on another well, the well annulus pressure must be
equalized before releasing the hanger, usually by killing the well.
There are advantages associated with being able to safely remove
the rotator such as for servicing, installing other equipment such
as a blowout preventor (BOP), or in full well servicing situations
to be able to pull the tubing string and rotatable tubing hanger
through the installed wellhead components.
[0006] Safety is enhanced if the tubing hanger continues to be
restrained to the casing bowl head during servicing so as to avoid
a pressure surge and violent ejection of the tubing. Of these two
components, the rotator is the most expensive. Accordingly, from an
economic aspect, and safe and convenient removal or replacement is
desirable.
[0007] Some assemblies separate the bowl and hanger from the more
expensive rotator component. These known arrangements are also
associated with several disadvantages; typically at least a portion
of the weight of the tubing is supported by the rotator, a
requirement being that the resulting rotator be robust such as
being fitted with thrust bearings capable of supporting tubing
loads, and all of which contribute to a large and tall
assembly.
[0008] For example in U.S. Pat. No. 5,429,188 to Cameron, a rotator
is housed in an assembly which can be removed from the wellhead
without affecting the tubing hanger. A two-piece rotating tubing
hanger comprises an outer sleeve and an inner mandrel rotatably
supported on bearings mounted in the outer sleeve, The tubing
string is suspended from the mandrel. The outer sleeve can be
secured to the wellhead using the holddown screws however the inner
mandrel is not restrained against annulus pressure.
[0009] Similarly, in U.S. Pat. No. 5,465,788 to Wright, a two-piece
hanger is fitted to the casing bowl. Tubing is suspended from an
inner mandrel which is supported on bearings supported in a outer
sleeve secured therein using the bowl's holddown screws. Wright
uses an independent tubular rotor shaft extending upwardly from the
mandrel and is rotatably secured thereto using splines. A
complicated assembly results between the rotator and the tubing
hanger in the accommodation of a mandrel retainer, and an
insertable key/keyway to prevent rotation and enable threading of
pickup tubing. The rotor shaft must be removed before the tubing
string can be lifted from the well.
[0010] Even though others have separated the hanger and rotator,
applicant is not aware of hanger assemblies in which the components
can be safely retained in the casing bowl if the rotator is
removed, where the hanger can be readily lifted from the bowl for
maintenance, or where the rotator can be easily retrofitted for
adding supplemental wellhead components. The present invention
provides an improved rotator and an improved hanger which avoid the
disadvantages of the prior art.
SUMMARY OF THE INVENTION
[0011] In a preferred aspect of the invention, a rotator and hanger
system is provided comprising a two-piece hanger having a dognut
sleeve adapted to fit a conventional tapered casing bowl and a
hanger mandrel rotatably supported in the dognut sleeve. A string
of production tubing is suspended from a lower end of the hanger
mandrel and an upwardly projecting shoulder at an upper end of the
hanger mandrel can be engaged by the holddown screw for restraining
backspin rotation of the tubing or for preventing ejection of the
tubing. The system further comprises a low profile rotator mounted
to the wellhead flange. An upper mandrel is threaded into the
hanger mandrel and extends upwardly to couple the rotator and
hanger. The rotator has a bore fitted with a drive collar which is
splined to a driven ring gear and splined to the upper mandrel for
coupling to hanger while eliminating thrust loads from the tubing.
Seals between the rotator bore, the collar and the upper mandrel
ensure isolation of the rotator and wellhead from the casing
bowl.
[0012] The preferred system is a simplified and inexpensive
assembly which permits the rotator to be safely removed or for
additional wellhead equipment to be mounted thereto, all without
risk of a blowout. The novel tubing hanger enables use of the
holddown screws during servicing to prevent rotation of the tubing
hanger (for making up threaded joints and for restraining hazardous
backspin) and to prevent accidental ejection of the tubing upon
removal of the rotator. Supporting the production tubing weight
elsewhere enables the manufacture of a very low profile rotator.
Further, the use of a upper mandrel which is threaded at it's upper
and lower ends results in an inexpensive assembly and enables
connection of threaded pulling tools.
[0013] According to one broad aspect of the invention there is
provided a novel and safe rotating hanger for suspending a string
of tubing from a casing bowl fitted with holddown screws
comprising:
[0014] a dognut sleeve having a bore and an outer profile
compatible for support in the casing bowl and sealing thereto;
and
[0015] a tubular hanger mandrel fitted rotatably to the dognut
sleeve's bore and having a lower end from which the tubing string
is suspended and an upper end projecting upwardly above the dognut
sleeve for forming an upper shoulder so that the holddown screws
can be actuated to a first position to engage the hanger mandrel's
upper shoulder for restraining rotation and preventing ejection
from the casing bowl, and to another position to disengage from the
upper shoulder so that hanger mandrel is free to rotate; and to
another position to disengage further from the upper shoulder so
that the hanger mandrel and dognut sleeve can be removed from
casing bowl.
[0016] The hanger mandrel can be locked down using the holddown
screws so that the rotator can be removed safely, namely without
risk of the hanger backspin, ejection from the casing bowl or
leakage.
[0017] Preferably, the tubular hanger mandrel is threaded in its
bore at the upper end for connection of threaded pulling tools.
[0018] More preferably, a tubular connector sub is provided
comprising an upper mandrel for coupling the rotating tubing hanger
and a rotator. This upper mandrel enables rotational coupling
without imposing tubing string thrust into the rotator which
enables use of smaller and more economical rotators. The upper
mandrel is threaded at a lower end to the hanger mandrel and is
splined at an upper end for rotational-only coupling with a
rotator. If the tubing needs to be removed, a retrieving tool can
be threaded to the upper end of the connector sub for lifting the
connecting sub, rotatable mandrel and suspended tubing string from
the well.
[0019] Further benefits are obtained using a low profile rotator
which bears no tubing thrust, isolates the wellhead from the casing
bowl, and provides onsite flexibility for various threaded or
flanged wellhead configurations. A preferred rotator has a flange
housing for mounting to the wellhead flange, said housing having a
bore therethrough and a concentric counterbore extending upwardly
from a lower mounting face. A concentric drive ring is supported in
the counterbore by a retaining ring and is fitted with internal
spline for rotational coupling with a collar. The collar is splined
inside and out for coupling to the ring gear and to the upper
mandrel. A drive gear is fitted to the housing to engage the drive
ring. Due to the use of a splined collar to decouple thrust loads,
the gear ring need only be lightly supported on bushings. The
collar is fitted with seals on its outer surface above and before
the ring gear splines to seal to rotator housing. The collar is
also fitted with a seal at its inside surface above the upper
mandrel splines.
[0020] Accordingly, an improved well tubing rotator and hanger
system is provided for a wellhead having a casing bowl, a wellhead
flange, and holddown screws. said system comprising a rotatable
two-piece tubing hanger having the hanger mandrel which can be
engaged and disengaged by the holddown screws, a tubular connector
sub threaded to the hanger mandrel and a rotator splined to the
connector sub.
[0021] The rotator itself is a unit which is independent of the
rotatable hanger. The rotatable hanger supports the loads of the
tubing string and the splined connector sub prevents any loads from
being transferred to the rotator. As the rotator does not support
any tubing loads, it can be very small, required only to provide
high-ratio incremental rotation. This rotator can be manufactured
with a very low profile, for example as low as 3-1/4 inches (8.3
cm), so that the rotator height only adds minimally to the overall
wellhead height.
[0022] In preferred embodiments, the tubing rotator is convertible
between accepting threaded production tubing to the flow tee or
being mountable to a blowout preventor (BOP) when necessary, for
example, in the event that the tubing becomes stuck. Such a
preferred tubing rotator adaptable to a flange-mounting comprises a
housing having an upper surface with threaded nozzle connection for
threaded wellhead components and wherein the ring gear, drive gear
and collar are located lower than the upper surface so that the
threaded connection can be machined off for forming a flange for
fifting of flanged components such as a BOP.
[0023] The apparatus and system described above enable a novel
method for safely servicing a well's wellhead while avoiding a
blowout, the wellhead being fifted with a tubing rotator and a
casing bowl fitted with holddown screws, the method comprising:
[0024] providing a two-piece rotating hanger comprising a dognut
sleeve having a bore and an outer profile which is compatible for
support in the casing bowl and sealing thereto, and a tubular
hanger mandrel fifted rotatably to the dognut sleeve's bore, the
mandrel having a lower end from which a tubing string is suspended
and an upper end projecting upwardly above the dognut sleeve for
forming an upper shoulder and connected drivably to the tubing
rotator;
[0025] actuating the holddown screws to a first position to engage
the hanger mandrel's upper shoulder for safely restraining rotation
and preventing ejection of the rotating hanger from the casing
bowl; and
[0026] removing the tubing rotator.
[0027] Preferably any stored rotational energy in the tubing string
can be relieved by actuating the holddown screws, disengaging from
the upper shoulder so that hanger mandrel is free to rotate. Once
the well has been hydraulically killed or the annulus has otherwise
been rendered safe from differential gas pressure, the rotating
hanger and tubing string can be safely retrieved. This can be done
with or without the rotator in place. Following the method above,
with the rotator removed, the holddown screws are disengaged
further from the upper shoulder and so that the hanger mandrel and
dognut sleeve can be removed fully from casing bowl.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 is cross-sectional view of a hanger and rotator of
one embodiment of the present invention;
[0029] FIG. 2 is a cross-sectional view of another embodiment of
the invention; and
[0030] FIG. 3 is an exploded cross-sectional view of the embodiment
of FIG. 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0031] Having reference to FIG. 1, a portion of a wellhead 10 is
illustrated having a casing bowl 11 secured at the ground surface
at the top of casing 12. The casing bowl 11 is a fitting having an
upwardly diverging bore 13 for forming the bowl. About the casing
bowl 11 is a wellhead flange 14. A rotatable tubing hanger 15 is
fitted to the casing bowl 11 and comprises a two-piece assembly of
a tubular dognut sleeve 16 and a rotatable hanger mandrel 17. The
dognut sleeve 16 has a bore 16b and an outer profiled surface 18
which is compatible with the casing bowl 11. One or more
circumferential seals 19, such as O-rings, seal between the dognut
sleeve's outer surface 18 and the bowl 11 and additional
circumferential seals 19b seal between the hanger mandrel dognut
sleeve, all of which sealing the well annulus 20 from the wellhead
10. The flange 14 is fitted with a plurality of bolt holes 21 for
attachment of various wellhead components (not shown).
[0032] The hanger mandrel 17 has a lower threaded end 30 for
connection to, and for suspending, a string of production tubing
31. The hanger mandrel 17 is a tubular member having a bore 17b
therethrough for passing production fluids from the tubing 31
through the tubing hanger 15 to the wellhead 10. At an upper end 32
of the hanger mandrel 17, the bore 17b is threaded for connection
to a variety of components as described later. The hanger mandrel's
upper end 32 further comprises a beveled upper shoulder 33 which
projects above the dognut sleeve 16 so that it can be engaged by
holddown screws 34.
[0033] An upward facing shoulder 35 is formed in the dognut
sleeve's bore 16b for supporting a thrust bearing 36. The hanger
mandrel's bore 17b has a corresponding downward facing shoulder 37
which bears against the thrust bearing 36. An annular groove and
snap ring 38 retain the hanger mandrel 17 and dognut sleeve 16
together. Accordingly, the hanger mandrel 17 is rotatable relative
to the non-rotating dognut sleeve 16. The holddown screws 34 are
adjustable between a first engaged position which engages the
hanger mandrel's beveled shoulder and which restrains both rotation
of the hanger mandrel and ejection of the production tubing (FIG.
2), a second disengaged position to release the hanger mandrel so
as to permit rotation (FIG. 1), and a third fully disengaged
position to enable removal of the entire rotating tubing hanger and
tubing from the casing bowl 11 (not shown).
[0034] A rotator 40 is adapted for mounting to the wellhead flange
11. The rotator 40 comprises a squat metallic cylindrical housing
41 forming a flange 42 of relatively low height. A ring of bolt
holes 43 are positioned about the periphery of the housing 41 which
correspond to the wellhead flange 14.
[0035] The rotator 40 has a lower face 44 which is compatible for
mounting to the wellhead flange 14 and an upper face 45 having a
periphery which is compatible for mounting with other flanged
wellhead components such as a BOP. The housing 41 has a bore 46
extending from the lower to the upper faces 44, 45 for conducting
fluids from the production tubing 31.
[0036] In the embodiment illustrated in FIG. 1, a threaded nozzle
50 is provided at the upper face 45 for connection of the rotator's
bore 46 to wellhead components such as a threaded rod BOP or a flow
tee. Further, a gasket 47 is fitted between the lower face 45 and
the wellhead flange 14. A fluid passage 48 enables fluid access to
the casing bowl 11.
[0037] Best seen in FIG. 3, rotator components are housed within an
annular drive cavity or counterbore 60 formed in the housing's bore
46. The counterbore 60 extends upwardly from the lower face 44 and
terminates at a top shoulder 61. A ring gear 62 is located
concentrically within the counterbore 60. A drive gear such as a
worm gear 63 extends transversely through the housing 41 and
intercepts the periphery of the counterbore 60 for engaging the
ring gear 62 tangentially. The ring gear 62 is aligned with the
worm gear 63 and restrained in the counterbore 60 with a lower
retainer ring 64 such as a snap ring.
[0038] A connector sub 70 is provided which comprises a tubular
upper mandrel 71 which extends between the hanger mandrel 17 and
the rotator's ring gear 62. A lower end 72 of the upper mandrel 71
is threaded into the hanger mandrel 17 for co-rotation. Use of
threaded connection significantly reduces manufacturing cost. The
holddown screws 34 can be actuated to engage the hanger mandrel's
beveled upper shoulder 33 for locking its rotation and permitting
making up and breaking of the threaded connection 72, 32. The upper
shoulder has a profile, beveled is shown, that permits engagement
of the holddown screw to both lock rotation relative to the casing
bowl and to interfere and prevent lifting or ejection of the hanger
mandrel 17 from the casing bowl. If the hanger mandrel 17 is
restrained from ejection, so is the dognut sleeve 16 and string of
tubing 31.
[0039] A cylindrical collar 80, having inner and outer surfaces 81,
82 fitted with inside splines 81a and outside splines 82a
respectively, is fitted in an annular space between the ring gear
62 and the connector sub 70 so that rotation of the ring gear 62
drives the collar 80 which drives the upper mandrel 71, hanger
mandrel 71 and production tubing 31.
[0040] Typically the production tubing 31 is only rotated at speeds
of 1-6 revolutions per day. Accordingly, the ring gear 62 only
needs to be supported sufficiently to counter reactive drive
forces. The ring gear 62 is sandwiched between thin upper and lower
bearing surfaces 83, 84 or bushings contributing to an
exceptionally low profile for the flange 42. The lower bearing
surface 84 is supported by an annular seal ring 85 which is secured
in the counterbore 60 by the retainer 64.
[0041] To facilitate isolation of the casing bowl 11 and the
remainder of the wellhead 10, various seals are provided between
the rotator 40, the collar 80 and the upper mandrel 71. The annular
seal ring 85 is fitted with an inner O-ring seal 90 which seals
against a lower depending cylindrical seal surface 81 of the collar
80, and seals with an outer O-ring seal 91 against the bore of the
rotator counterbore 60, thereby isolating the rotator components
from the casing bowl 11. Similarly, an O-ring seal 92 between an
upper cylindrical seal surface 82 of the collar 80 and the upper
mandrel 71. Lastly an O-ring seal 93 is provided between the collar
80 and the rotator bore 46 adjacent the upper face 45.
[0042] In another embodiment illustrated in FIG. 2, the upper face
of the rotator is flanged, not threaded. The upper face 45 and
rotator flange 42 can be manufactured as such or is convertible
from the threaded nozzle-fitted rotator of FIG. 1. A conversion is
possible by locating the ring gear 62 lower than the upper face 45
so that the threaded nozzle 50 of FIG. 1 can be removed by
machining, even while on site, for fitting of a flanged BOP of
other flanged component. A gasket groove 95 can be also machined in
the upper face. 45
[0043] Referring back to FIG. 1 as demonstrative of rotating
operation, the holddown screws 34 are actuated, backing them off
slightly to a least a first position to enable the hanger mandrel
to rotate. Operation of the worm gear 63 rotates the ring gear 62
and collar 80. The collar 80 drives the upper mandrel 71 which
rotates the hanger mandrel 17 and suspended production tubing
31.
[0044] The rotator 40 is removed for servicing, or for access to
the production tubing 31. The nature of the worm gear 63 or the
high reduction between a drive gear and ring gear 62 usually
prevents controlled back-rotation of the production tubing 31.
Accordingly, there can be stored rotational energy in the wound up
production tubing 31 which can result in a violent backspin upon
removal of the rotator 40. The safest approach is to engage the
holddown screws and upper shoulder 33, thereby locking the hanger
mandrel 17 against backspin rotation before releasing the rotator
40.
[0045] As shown in the exploded view of FIG. 3, once the holddown
screws are engaged, the rotator 40 can be safely unbolted from the
casing bowl flange 14 and lifted free. The upper mandrel 71 can be
left in place or unthreaded for connection of a handling sub or
other tool for retrieving the production tubing.
[0046] Should a rotator 40 no longer be required, this expensive
piece of hardware can be removed for reuse elsewhere while leaving
or abandoning the inexpensive two-piece tubing hanger 15 in
place.
* * * * *